#include "string.h"
namespace MyString
{
	const size_t string::npos = -1;

	void string::reserve(size_t n)
	{
		if (n > _capacity)
		{
			char* tmp = new char[n + 1];
			strcpy(tmp, _str);
			delete[] _str;
			_str = tmp;
			_capacity = n;
		}
	}

	void string::push_back(char ch)
	{
		if (_size == _capacity)
		{
			reserve(_capacity == 0 ? 4 : _capacity * 2);
		}
		_str[_size] = ch;
		++_size;
		_str[_size] = '\0';
	}

	void string::append(const char* str)
	{
		size_t len = strlen(str);
		if (len + _size > _capacity)
		{
			reserve(len + _size > 2 * _capacity ? len + _size : 2 * _capacity);
		}
		strcpy(_str + _size, str);
		_size += len;
	}

	string& string::operator+=(char ch)
	{
		push_back(ch);
		return *this;
	}
	string& string::operator+=(const char* str)
	{
		append(str);
		return *this;
	}

	void string::insert(size_t pos, char ch)
	{
		assert(pos <= _size);
		if (_size == _capacity)
		{
			reserve(_capacity == 0 ? 4 : 2 * _capacity);
		}
		size_t end = _size + 1;
		while (pos < end)
		{
			_str[end] = _str[end - 1];
			--end;
		}
		_str[pos] = ch;
		++_size;
	}

	void string::insert(size_t pos, const char* str)
	{
		assert(pos <= _size);
		size_t len = strlen(str);
		if (len == 0)
			return;
		if (len + _size > _capacity)
		{
			reserve(len + _size > 2 * _capacity ? len + _size : 2 * _capacity);
		}
		size_t end = _size + len;
		while (pos + len - 1 < end)
		{
			_str[end] = _str[end - len];
			--end;
		}
		for (int i = 0;i < len;i++)
		{
			_str[pos+i] = str[i];
		}
		_size += len;
	}

	void string::erase(size_t pos, size_t len)
	{
		assert(pos <= _size);
		if (len >= _size - pos)
		{
			_size = pos;
			_str[pos] = '\0';
		}
		else
		{
			for (size_t i = pos + len;i < _size;i++)
			{
				_str[i - len] = _str[i];
			}
			_size -= len;
		}
	}

	size_t string::find(char ch, size_t pos)
	{
		assert(pos < _size);
		for (int i = pos; i < _size; i++)
		{
			if (_str[i] == ch)
				return i;
		}
		return npos;
	}

	size_t string::find(const char* str, size_t pos)
	{
		assert(pos < _size);
		const char* ptr = strstr(_str + pos, str);
		if (ptr == nullptr)
			return npos;
		else
			return ptr - _str;
	}

	string string::substr(size_t pos, size_t len)
	{
		if (pos + len > _size)
		{
			len = _size - pos;
		}
		string sub;
		sub.reserve(len);
		for (size_t i = 0;i < len;i++)
		{
			sub[i] = _str[pos + i];
		}
		return sub;
	}
	
}